Vaccination against pathogens has been one of the major accomplishments of medicine over the past century. While effective vaccines have been developed for a large number of diseases, development of safe and effective vaccines for a number of other diseases remains problematic. For example, the use of inactivated or killed microbial agents as a vaccine, although generally safe, will not always be effective if the immunogenic characteristics of the agent are altered. Indeed, the preferential degradation of certain antigens on the inactivated microorganisms might produce a weak or poorly targeted immune response that permits a pathological course when the host is later exposed to the live microorganism. In addition, while the preparation of live attenuated microbial agents as vaccines will often provide improved immunologic reactivity, use of such live attenuated microbial agents has an increased risk that the vaccine itself will be infectious. Such live attenuated vaccines can be infectious, for example, if mutation or reversion occurs, because the organism may be able to propagate and provide a reservoir for future infection.
Thus, one must often choose between improved effectiveness and greater degree of safety when selecting between the viral inactivation and viral attenuation techniques for vaccine preparation. The choice is particularly difficult when the virus is resistant to inactivation and requires rigorous inactivation conditions that are likely to degrade the antigenic characteristics.
Therefore improved methods for inactivating viruses are desirable, where the methods are capable of completely inactivating viruses without causing substantial degradation of the antigenic structure of these viruses. In particular, the inactivated viruses should be useful as vaccines and free from adverse side effects at the time of administration as well as upon subsequent challenge with the live infectious agent.
It is also desirable to provide improved methods for inactivating agents such as bacteria, cancer cells, and other cell types, where the methods are capable of inactivating these agents without causing substantial degradation of the antigenic structure of the agents. In particular, the inactivated agents should be useful as vaccines and free from adverse side effects at the time of administration, as well as upon subsequent challenge with the live agent.